Field
This disclosure relates to a rechargeable battery having flexibility.
Description of the Related Technology
In accordance with the development of a technology for mobile devices, a demand for a rechargeable battery as an energy source has increased. The rechargeable battery is a battery repeatedly charged and discharged unlike a primary battery.
A small capacity rechargeable battery may be used in a small portable electronic device such as a mobile phone, a laptop computer, and a camcorder, and a large capacity rechargeable battery may be used as a power supply for driving a motor of a hybrid vehicle and an electric vehicle.
For example, a pouch type rechargeable battery includes a stacked type electrode assembly performing a charging and discharging operation, a pouch accommodating the electrode assembly and an electrolyte therein, and electrode tabs leading the electrode assembly to the outside of the pouch.
The stacked type electrode assembly is formed by repeatedly stacking units, wherein each stack each includes a negative electrode, a separator, a positive electrode, and a separator and is led to the outside of the pouch by the electrode tabs welded to uncoated parts of the negative and positive electrodes.
As for the sizes of the positive electrode, the negative electrode, the separator, and the pouch in the rechargeable battery to which the stacked type electrode assembly is applied, size of the negative electrode is larger than that of the positive electrode and size of the separator is equal to or larger than that of the negative electrode, and size of the pouch is larger than that of the separator.
The size of the negative electrode should be larger than that of the positive electrode in order for lithium ions moving at the outermost portion of the positive electrode not to be precipitated on the outer side of the negative electrode at the time of charging the rechargeable battery. The size of the separator should be larger than that of the positive electrode and be at least equal to that of the outermost portion of the negative electrode or larger than that of the negative electrode in order to physically separate the positive electrode and the negative electrode from each other.
In order to satisfy the above-mentioned relationships and secure energy density of the rechargeable battery, size differences between the positive electrode and the negative electrode, between the negative electrode and the separator, and the positive electrode and the separator, need to be minimized.
As an example, in the pouch type rechargeable battery, size differences among the negative electrode, the separator, and the positive electrode are appropriately set so that an internal short-circuit due to a direct contact between the positive electrode and the negative electrode is not generated even though external impact is applied to the electrode assembly due to vibrations, and the like.
Typically a problem does not occur when the form of a pouch type rechargeable battery is maintained. But when the positive electrode and the negative electrode disposed in the pouch type rechargeable battery move as the form of the rechargeable battery is bent, it can result in an internal short-circuit. In addition, in cases where the internal short-circuit is severe, explosion and a fire may occur in the pouch type rechargeable battery.